first, allow ADB debugging on your phone by developer options (how to get to developer options is different in every phone so let me know which phone you have)
then go to webadb.com connect your phone with your computer, on webadb.com klick connect device, allow the connection on your phone, then go to interactive shell, and copy-paste these commands (every line separately)
to be clear I'm assuming you what to use apps4flip mouse,
and also only app4flip mouse, not voice accuses and mouse (if you want both please let me know the codes are different)
pm uninstall -k --user 0 com.lge.voicecommand
appops set com.android.cts.appsflipcursor SYSTEM_ALERT_WINDOW allow
settings put secure accessibility_enabled 1
settings put secure enabled_accessibility_services com.android.cts.appsflipcursor/com.android.cts.appsflipcursor.services.MouseEventService
am startservice com.android.cts.appsflipcursor/com.android.cts.appsflipcursor.services.MouseEventService